Role of heart rate variability in the early diagnosis of diabetic autonomic neuropathy in children

BACKGROUND: Diabetic autonomic neuropathy (DAN) is a major complication of diabetes. DAN has been shown to be closely related to glycemic control. To contribute significantly to the morbidity and mortality of the disease, and to be indicative of an increased risk of cardiovascular events. Tests assessing the function of the autonomic nervous system, such as the response of heart rate and blood pressure to maneuvers stimulating the autonomic nervous system, including deep breathing. Valsalva maneuver and standing, allowed to detect signs of DAN in adolescents; however, the sensitivity of such tests in revealing an early impairment of the autonomic nervous system proved low. Several studies found heart rate variability (HRV) to be useful in assessing the dysfunction of the autonomic nervous system in diabetic children and adolescents, but only few HRV parameters were evaluated in most of them. OBJECTIVE: To study cardiac autonomic nervous system in diabetic children, and to investigate whether the duration of diabetes and the degree of metabolic control are determinants for the development of DAN in children. PATIENTS AND METHODS: We analyzed HRV in 50 asymptomatic patients with insulin-dependent diabetes mellitus (IDDM) and 30 healthy children matched for age and sex. RESULTS: Patients with a history of diabetes > 8 years showed significant alterations of the autonomic nervous system (significant reduction of r-MSSD, pNN50, HF and increase in LF/HF). Conversely, only a reduction in pNN50 was found in patients with a disease duration < 8 years. Furthermore, we also observed significant HRV abnormalities in patients with an impaired metabolic control of diabetes. Compared to controls, patients with glycosylated hemoglobin blood levels (HbA(1C)) > 8% showed a significant reduction of r-MSSD, pHH50 and total power spectrum, whereas no HRV abnormalities were detected in patients with an HbA(1C) < 8%. CONCLUSIONS: HRV analysis can detect early subclinical alterations of the autonomic nervous system in asymptomatic patients with IDDM, which seem to consist mainly in a parasympathetic impairment. Autonomic dysfunction is associated both with the duration and an inadequate metabolic control of the disease.